diff --git a/src/ipv4/static_ipv4.ml b/src/ipv4/static_ipv4.ml
index 8f7f6a65e..761353b9a 100644
--- a/src/ipv4/static_ipv4.ml
+++ b/src/ipv4/static_ipv4.ml
@@ -176,6 +176,6 @@ module Make (R: Mirage_random.S) (C: Mirage_clock.MCLOCK) (Ethernet: Mirage_prot
 
   let src t ~dst:_ = Ipaddr.V4.Prefix.address t.cidr
 
-  let mtu t = Ethernet.mtu t.ethif - Ipv4_wire.sizeof_ipv4
+  let mtu t ~dst:_ = Ethernet.mtu t.ethif - Ipv4_wire.sizeof_ipv4
 
 end
diff --git a/src/ipv6/ipv6.ml b/src/ipv6/ipv6.ml
index 40c16a65e..83292a660 100644
--- a/src/ipv6/ipv6.ml
+++ b/src/ipv6/ipv6.ml
@@ -61,7 +61,7 @@ module Make (N : Mirage_net.S)
     in
     loop (Some u)
 
-  let mtu t = E.mtu t.ethif - Ipv6_wire.sizeof_ipv6
+  let mtu t ~dst:_ = E.mtu t.ethif - Ipv6_wire.sizeof_ipv6
 
   let write t ?fragment:_ ?ttl:_ ?src dst proto ?(size = 0) headerf bufs =
     let now = C.elapsed_ns () in
diff --git a/src/stack-direct/tcpip_stack_direct.ml b/src/stack-direct/tcpip_stack_direct.ml
index dfbc0340c..b7f528942 100644
--- a/src/stack-direct/tcpip_stack_direct.ml
+++ b/src/stack-direct/tcpip_stack_direct.ml
@@ -376,9 +376,9 @@ module IPV4V6 (Ipv4 : Mirage_protocols.IPV4) (Ipv6 : Mirage_protocols.IPV6) = st
     List.map (fun ip -> Ipaddr.V4 ip) (Ipv4.get_ip t.ipv4) @
     List.map (fun ip -> Ipaddr.V6 ip) (Ipv6.get_ip t.ipv6)
 
-  let mtu t =
-    (* TODO incorrect for IPv4 *)
-    Ipv6.mtu t.ipv6
+  let mtu t ~dst = match dst with
+    | Ipaddr.V4 dst -> Ipv4.mtu t.ipv4 ~dst
+    | Ipaddr.V6 dst -> Ipv6.mtu t.ipv6 ~dst
 end
 
 module MakeV4V6
diff --git a/src/stack-unix/ipv4_socket.ml b/src/stack-unix/ipv4_socket.ml
index 790a6bccf..ecd2fae70 100644
--- a/src/stack-unix/ipv4_socket.ml
+++ b/src/stack-unix/ipv4_socket.ml
@@ -22,7 +22,7 @@ type callback = src:ipaddr -> dst:ipaddr -> Cstruct.t -> unit Lwt.t
 let pp_error = Mirage_protocols.Ip.pp_error
 let pp_ipaddr = Ipaddr.V4.pp
 
-let mtu _ = 1500 - Ipv4_wire.sizeof_ipv4
+let mtu _ ~dst:_ = 1500 - Ipv4_wire.sizeof_ipv4
 
 let disconnect _ = Lwt.return_unit
 let connect _ = Lwt.return_unit
diff --git a/src/stack-unix/ipv4v6_socket.ml b/src/stack-unix/ipv4v6_socket.ml
index f8c49910c..3f31ebbf1 100644
--- a/src/stack-unix/ipv4v6_socket.ml
+++ b/src/stack-unix/ipv4v6_socket.ml
@@ -22,7 +22,9 @@ type callback = src:ipaddr -> dst:ipaddr -> Cstruct.t -> unit Lwt.t
 let pp_error = Mirage_protocols.Ip.pp_error
 let pp_ipaddr = Ipaddr.pp
 
-let mtu _ = 1500 - Ipv6_wire.sizeof_ipv6
+let mtu _ ~dst = match dst with
+  | Ipaddr.V4 _ -> 1500 - Ipv4_wire.sizeof_ipv4
+  | Ipaddr.V6 _ -> 1500 - Ipv6_wire.sizeof_ipv6
 
 let disconnect _ = Lwt.return_unit
 let connect _ = Lwt.return_unit
diff --git a/src/stack-unix/ipv6_socket.ml b/src/stack-unix/ipv6_socket.ml
index 9507ec7b6..b9811e82c 100644
--- a/src/stack-unix/ipv6_socket.ml
+++ b/src/stack-unix/ipv6_socket.ml
@@ -23,7 +23,7 @@ type callback = src:ipaddr -> dst:ipaddr -> Cstruct.t -> unit Lwt.t
 let pp_error = Mirage_protocols.Ip.pp_error
 let pp_ipaddr = Ipaddr.V6.pp
 
-let mtu _ = 1500 - Ipv6_wire.sizeof_ipv6
+let mtu _ ~dst:_ = 1500 - Ipv6_wire.sizeof_ipv6
 
 let disconnect () = Lwt.return_unit
 let connect () = Lwt.return_unit
diff --git a/src/tcp/flow.ml b/src/tcp/flow.ml
index f74fbe21d..f4a80fc55 100644
--- a/src/tcp/flow.ml
+++ b/src/tcp/flow.ml
@@ -316,7 +316,7 @@ struct
   let emitted_keepalive_warning = ref false
 
   let new_pcb t params id keepalive =
-    let mtu_mss = Ip.mtu t.ip - Tcp_wire.sizeof_tcp in
+    let mtu_mss = Ip.mtu t.ip ~dst:(WIRE.dst id) - Tcp_wire.sizeof_tcp in
     let { tx_wnd; sequence; options; tx_isn; rx_wnd; rx_wnd_scaleoffer } =
       params
     in
@@ -413,7 +413,7 @@ struct
     Hashtbl.add t.listens id (params.tx_isn, (pushf, (pcb, th)));
     Stats.incr_listen ();
     (* Queue a SYN ACK for transmission *)
-    let options = Options.MSS (Ip.mtu t.ip - Tcp_wire.sizeof_tcp) :: opts in
+    let options = Options.MSS (Ip.mtu t.ip ~dst:(WIRE.dst id) - Tcp_wire.sizeof_tcp) :: opts in
     TXS.output ~flags:Segment.Syn ~options pcb.txq (Cstruct.create 0) >>= fun () ->
     Lwt.return (pcb, th)
 
@@ -685,7 +685,7 @@ struct
     (* TODO: This is hardcoded for now - make it configurable *)
     let rx_wnd_scaleoffer = wscale_default in
     let options =
-      Options.MSS (Ip.mtu t.ip - Tcp_wire.sizeof_tcp) :: Options.Window_size_shift rx_wnd_scaleoffer :: []
+      Options.MSS (Ip.mtu t.ip ~dst - Tcp_wire.sizeof_tcp) :: Options.Window_size_shift rx_wnd_scaleoffer :: []
     in
     let window = 5840 in
     let th, wakener = MProf.Trace.named_task "TCP connect" in
diff --git a/tcpip.opam b/tcpip.opam
index 8e6814ddc..950fa30fd 100644
--- a/tcpip.opam
+++ b/tcpip.opam
@@ -29,7 +29,7 @@ depends: [
   "mirage-clock" {>= "3.0.0"}
   "mirage-random" {>= "2.0.0"}
   "mirage-stack" {>= "2.2.0"}
-  "mirage-protocols" {>= "4.0.0"}
+  "mirage-protocols" {>= "5.0.0"}
   "mirage-time" {>= "2.0.0"}
   "ipaddr" {>= "5.0.0"}
   "macaddr" {>="4.0.0"}
@@ -48,7 +48,7 @@ depends: [
   "pcap-format" {with-test}
   "mirage-clock-unix" {with-test & >= "3.0.0"}
   "mirage-random-test" {with-test & >= "0.1.0"}
-  "arp-mirage" {with-test & >= "2.0.0"}
+  "arp" {with-test & >= "2.3.0"}
   "ipaddr-cstruct" {with-test}
   "lru" {>= "0.3.0"}
 ]
@@ -63,6 +63,3 @@ system](https://mirage.io). It provides implementations for the following module
 * UDP
 * TCP
 """
-pin-depends: [
-  [ "mirage-protocols.5.0.0" "git+https://github.com/hannesm/mirage-protocols.git#208f364329a6b3f6026fa361d89db66dbac4e37a" ]
-]
diff --git a/test/dune b/test/dune
index f288e3c75..31b26afac 100644
--- a/test/dune
+++ b/test/dune
@@ -2,7 +2,7 @@
  (name test)
  (libraries alcotest mirage-random-test lwt.unix logs logs.fmt mirage-profile
    mirage-flow mirage-vnetif mirage-clock-unix pcap-format duration
-   mirage-random rresult mirage-protocols mirage-stack arp arp-mirage
+   mirage-random rresult mirage-protocols mirage-stack arp arp.mirage
    ethernet tcpip.ipv4 tcpip.tcp tcpip.udp tcpip.stack-direct tcpip.icmpv4
    tcpip.udpv4-socket tcpip.tcpv4-socket tcpip.icmpv4-socket
    tcpip.stack-socket tcpip.ipv6 ipaddr-cstruct macaddr-cstruct tcpip.unix)